This study proposes to identify one of the genes responsible for a form of preaxial polydactyly that can be inherited as an autosomal dominant trait. Preaxial polydactyly refers to an excess of digits on the thumb side of the limb. A large six-generation family was identified in which 20 individuals have preaxial polydactyly. Blood samples were obtained from multiple individuals in the family and DNA was extracted for genetic studies. Subsequent genetic mapping demonstrated that the gene responsible for this form of polydactyly resides.